Radials, the Comet GP-3, and the Diamond X50NA
- With no radials, impedance changes for both 2m and 440 were easily observable with varying hand positions.
- With seven inch radials, impedance changes for 440 were almost entirely eliminated. 2m impedance changes continued.
- With 20 inch radials, impedance changes for both 440 and 2m were almost entirely eliminated despite hand positions.
This suggests radials of 1/4 and 3/4 wavelength do a good job of immunizing the antenna from circumstances that might encourage rf currents down the mast or coax. Radials of 1/12 wavelength do nothing.
The antenna pattern was measured with the above three radial scenarios with a ferrite placed on the feedline about 66 inches below the antenna feedpoint. I will tell you more about the ferrite after presenting this…
About that ferrite
Key takeaways to ponder
- 7 inch radials don’t do much at 146 MHz.
- 20 inch radials do a lot for us at 146 MHz.
- Radials matter.
- There are plenty of installation cases where the mast or feedline circumstances do not try to steal gobs of current from your coax feed point therefore reducing the need for the radials, but this appears to be simply about luck.
- From our ferrite and hand placement experiments, I would think most folks might have significant rf currents down the mast/feed, say, 1/6 to 1/12 of the time. Roll a 6 on one die or snake-eyes on 2. Good odds.
- In our example, we only lost a dB or two due to currents on our mast/feed. No big deal to some, but… why did you spend $100 on an antenna? Among other things, a little more gain? If so, why accept a little more loss due to ineffective radials?
- In our example, the mast/feed is about 6 feet long. What happens when this changes to 20, 30, 40, etc. should be concerning… not good.